The invention relates to over-the-road trailers and rear impact guards thereof. A conventional trailer 1000 is shown in FIG. 1, and is configured for over-the-road use with a truck to transport large cargo volumes. The trailer 1000 has a defined front end 1020 adapted for attachment with the truck, and a defined rear end 1040 opposite the front end 1020. A front-rear, or lengthwise direction X is defined between the front and rear ends 1020, 1040, A transverse or lateral direction Y is defined perpendicular to the lengthwise direction X. The lengthwise and lateral directions Y are both parallel to a ground surface along which the trailer 1000 is conveyable. The rear end 1040 in many cases is provided with doors for accessing the cargo area defined between the front and rear ends 1020, 1040 (and between the sidewalls 1050 and roof 1060, if so equipped). At the rear end 1040 of the trailer, a rear impact guard 1100 is provided. The rear impact guard 1100 complies with federal mandates for many common types of trailers and is designed to reduce the severity of a crash when a vehicle following the trailer 1000 impacts the rear end 1040 of the trailer 1000. The rear impact guard 1100 provides a lowered bumper 1110 below the rear sill or rear bolster 1130 at the bottom rear end of the cargo area. However, it may be desirable to further improve safety, especially for off-center impacts, while minimizing cost and weight penalties to the trailer.